Fertility Flashcards
Oogenesis
Primordial germ cells invade genital ridge then become eggs/sperm, first identifiable at 3 weeks, undergoes many cycles of mitosis
Genital ridge becomes gonad, gonadal differentiation linked to PGC development
Oocyte Differentiation
Germ cells enter the ovary to become oogonia-egg precursors that divide by mitosis
Oogonia mitosis stops and enter meiosis to produce primary oocytes which are diploid
Mitotic divisions critical: No more oocytes made after
Primary oocytes remain in the first phase of meiosis until ovulation or cell death occurs
Primordial follicle
Oocyte surrounded by protective layers and cells
Surrounding cells condense around oocyte and differentiate into granulosa cells
Granulosa cells secrete basal lamina
Folliculogenesis
Growth and development of follicles from rest stages to ovulation
Oocyte secrete acellular layer-zona pellucida, stays attached after ovulation
Second layer of cells differentiate around basal layer to form theca cells
Follicle Growth
Driven mostly by FSH but early growth is independent of FSH
o Even with FSH suppression
• Rapid increase in Follicle diameter and increased Granulosa cell division lead to gaps to form between Granulosa layers
o Fluid-filled spaces forming an Antrum – Known as
Antral/Secondary Follicles
`Follicle Recruitment
Only follicles of sufficient size able to survive decrease in FSH (which occurs due to initial Negative Feedback from Oestrogen)
o Only one follicle from the pool will be selected for Ovulation and possible Fertilisation
Movement of sperm in female tract
Coagulation of seminal fluid to reduce sperm loss-liquefaction occurs later, sperm survive 24-48 hours in tract
Absence of progesterone means mucous is less viscous allowing sperm to pass
Movement through mucous leads to removal of seminal fluid and abnormal sperm
Sperm inhabit cervical crypts which act as a reservoir
Currents set up by uterine/tubal cilia, chemoattractant from oocyte cumulous complex
Sperm Capacitation
Biochemical arrangement of surface glycoproteins initiates whiplashing of sperm tail increasing progressive motility and preparing it for acrosomal reaction
Promoted through removal of sperm from seminal fluid, factors in uterine or tubal fluid
Fertilisation
Acrosomal membrane on the sperm head fuses when in close proximity to oocyte-release of enzymes which cut through outer layer of cumulus cells
Sperm head taken in by phagocytosis
Release of cortical granules of oocyte leading to hardening of oocyte to prevent polyspermy
Syngamy
Fusion of 2 gametes together
Entry of sperm causes oocyte intracellular Ca2+ influx
Oocyte completes meiosis 2 forming female pronucleus and expelling the second polar body
Break down of sperm nuclear membrane leading to decondensation of chromatin and separation of chromosomes forming male pronucleus and pronucleus membranes break down and first mitotic division occurs
Implantation
2 cell zygote, 4 cell, morula stage (8-16 cells, 3-4 days post), blastocyst stage
Zona hatching occurs in late blastocyst stage, loose apposition of blastyocyst with endometrial wall with direct contract with trophoblast and decidua leading to adhesion and invasion
Most common sites for ectopics: Tubal, cervical, ovarian or abdominal
Stats on Subfertility
1 in 6 couples seek specialist help
84% will achieve pregnancy in 1yr with regular UPSI, 92% within 2 years
Refer for specialist advice if at least 1 year of trying
Prompt investigations if known fertility issues, anovulatory cycles, severe endometriosis , previous PID, malignancy
Causes of subfertility
21% due to ovulation disorders 15-20% due to Tubal factors 6-8% Endometriosis 25% Male factors 28% Unexplained
Causes of Anovulation
Premature Ovarian Failure Turner's (Primary Amenorrhoea) Autoimmune Iatrogenic: Surgery/chemotherapy Secondary to PCOS Excessive weight loss or exercise Hypopituitarism Kallmann's Syndrome (Primary Hypogonadotropic Hypogonadism) Hyperprolactinaemia (Adenoma)
Assessment of Female Subfertility
Duration, menstrual cycle (regularity, LMP), pelvic pain (dysmenorrhoea, dyspareunia), cervical smear hx, previous pregnancies or ectopics, coital frequency
PMHx, PSHx, STIs, PID, DHx
Smoking, ETOH, Folic acid, rec drugs
Examine BMI, endocrine signs, pelvic exam, cervical smear and chlamydia screening
Investigations: Baseline (day 2-5) FSH, LH, TSH, Prolactin, Testosterone, Mid Luteal Progesterone
Assessment of Tubal Patency-Hysterosalpingography, Laparoscopy and Dye test or Hysterosalpingo contrast sonography
